Molecular recognition is the "...specific recognition of (and interaction with) one molecule by another"1. Two types of artificial molecules that exhibit molecular recognition will be presented here: Crown ethers, and Julius Rebek's self-replicating molecules. Crown ethers demonstrate specificity for shape as well as size and charge. Rebek's self-replicating molecules may model natural synthesis and replication. (1).
A crown ether is a cyclic, organic molecule containing ether groups. Simple crown ethers contain 9-18 carbon atoms. The lone pairs on the oxygen atoms are available to non-covalently bond metal ions. Crown ethers bond specifically, and may distinguish between a potassium and Sodium or Silver ions . The cavity of the crown ether is specific for shape, as well as charge and size. Azacrowns, are examples of more complex crown ethers, with nitrogen atoms participating in non-covalent interaction. (1).
Julius Rebek presents evidence for the synthesis of molecules that can self-replicate from component parts. A molecule made of two complementary parts serves as a template for replication. Specific binding of components (via hydrogen bonds) positions components to form a peptide bond. The strain of the system is relieved by the breaking of the relatively weak hydrogen bonds, and the newly synthesized molecule is released.(1)
1.Ball, P., Designing the Molecular World: Chemistry at the Frontier. Princeton university press, 1994. p145-185.
Lipkin,R., Darwin in Vitro: the quest to make synthetic molecules, Science News, vol.146,1994, p.362-363.
Rebek, J., Synthetic self-replicating molecules, Scientific American, July 1994, p.48-55.
Rebek research program web site
Ronald N. Warrenera, Richard A. Russellb, and Shudong Wanga, Crown Ether Isobenzofurans: Key Reagents in Supramolecular Chemistry Studies. http://www.cqu.edu.au/research/cma/ShudongWang
I wish to thank my fellow student Helen. We worked together on the project that got me interested in this topic. She may be reached at andehe00@dons.ac.usfca.edu
© 1997, 1998, 1999 krhenry@sirius.com
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